Gear recognition switch system

This application claims priority under 35 USC Section 119(e) (1) of provisional application No. 60/060,044 filed Sep. 25, 1997.

FIELD OF THE INVENTION

This invention relates generally to vehicular transmissions and more particularly to apparatus for sensing the position of the manual valve of an automatic transmission which determines the transmissions' mode at any given time.

BACKGROUND OF THE INVENTION

It is conventional to provide a switch assembly to receive mechanical gear selection inputs from the driver of a vehicle through various linkages and output electrical signals to the transmission electronic control unit indicative of the gear selections. Such switch assemblies generally comprise either a rotary movable contact mechanism such as those shown in U.S. Pat. Nos. 5,525,768 and 5,440,087, assigned to the assignee of the present invention, or a linear movable contact mechanism such as that shown in U.S. Pat. No. 5,231,254, also assigned to the assignee of the present invention. The present invention relates to the latter type in which an actuator carrying a set of movable contacts is caused to slide back and forth in dependence upon the longitudinal movement of the manual valve of the transmission. The movable contacts are spring biased into engagement with a stationary contact board having contact segments arranged in a selected pattern so that an on/off output signal is obtained based on the longitudinal position of the manual valve.

Typically, the actuator is held in place by a housing and some type of cover with clearance provided between the actuator, on the one hand, and the housing and cover on the other hand to permit the actuator to move with the manual valve. However, erratic and inconsistent voltage output signals have resulted from unintentional motion of the actuator due to the degree of motion available to the actuator. Clearances between the actuator and the housing and cover allow the actuator to move in all six directions of motion. Longitudinal, lateral and vertical translation together with pitch, yaw and roll motion alter the movable contact projection onto the stationary contacts thereby intensifying voltage drop irregularities. Also, as a result of vibration, the actuator will move within the associated clearances with sudden impacts between the actuator and the surrounding wall. This causes the contact mechanism to jump or bounce resulting in open signals. In addition, a more detrimental mode of failure can result after prolong vibration, that of contact wear. Vibration exacerbates the rubbing action of contacts against each other thereby breaking material, removing plating, if present, and roughening the interface. This action has been found to increase contact resistance from 1 ohm to as much as 700 ohms or more.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a gear recognition switch system which overcomes the above noted prior art limitations. Another object of the invention is the provision of a linear type gear recognition switch system which is less sensitive to vibration. Yet another object of the invention is the provision of a gear recognition switch system of the type described which is reliable and one which has improved contact life.

Other objects, advantages and details of the switch apparatus of this invention appear in the following detailed description of the preferred embodiment of the invention.

Briefly, in accordance with the invention, an actuator of a vehicular transmission gear recognition switch system mounts movable contacts which are adapted to slide into and out of engagement with stationary contact segments mounted in an associated housing in dependence upon the movement of the manual valve of the transmission. The actuator comprises integral, flexible members arranged to eliminate clearance between the actuator and the housing in two of three mutually perpendicular directions, the third mutually perpendicular direction being that of the intended motion of the actuator. A pair of beams of selected cross sectional area, one on either side of a manual valve engaging yoke, are formed by respective isolation slots in the base wall of the actuator with a projection formed centrally on each beam. The projections are adapted to be received on a platform surface of the housing and the compliant action of the beams eliminates vertical clearance when the beams are loaded upon assembly of the apparatus. An additional beam is located in the base wall on one side of the actuator by an isolation slot and is provided with a projection extended laterally outwardly from the side and which cooperates with spaced projections extending laterally outwardly from an opposite side of the actuator and which, when inserted in an opening in the housing, loads the additional beam in the lateral direction thereby eliminating lateral clearance. Elimination of the clearance in the vertical and lateral directions, while allowing longitudinal motion in dependence upon the longitudinal position of the manual valve of the transmission, results in elimination of contact chatter and enhancement of contact life in the gear recognition switch.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a perspective view of a gear recognition switch system made in accordance with the invention shown as it appears mounted in a schematically depicted vehicular transmission;

FIG. 2

is an exploded perspective view of the

FIG. 1

system along with a stylized showing of a manual valve member taken from a position slightly below the system;

FIG. 3

is an exploded perspective view of the

FIG. 1

system taken from a position slightly above the system;

FIG. 4

is a cross sectional view taken through the assembly in a direction perpendicular to the longitudinal axis of the manual shaft receiving opening of the actuator's yoke;

FIG. 5

is a top plan view of the

FIGS. 1-4

actuator;

FIG. 6

is a cross sectional view taken on line

6

—

6

of

FIG. 5

;

FIG. 7

is a bottom plan view of the

FIG. 5

actuator;

FIG. 8

is a perspective view of the actuator from a position above the actuator;

FIG. 9

is a perspective view of the actuator from a position below the actuator; and

FIG. 10

is a graph showing the voltage output signal of six different switches subjected to Z-axis vibration, switches

1

,

2

and

3

being prior art switches and switches

4

,

5

and

6

being made in accordance with the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

With reference to

FIG. 1

, a gear recognition switch system

10

made in accordance with the invention is shown mounted within a transmission housing and coupled to the manual valve member

12

of the transmission. System

10

is attached, as by suitable bolts (not shown) through bores

14

a

,

14

b

, to a wall of the transmission housing, removed for the purpose of illustration. System

10

provides an electrical output via pins

16

which is dependent upon the position of valve member

12

along the longitudinal axis

12

a

as will be discussed infra. As shown in

FIGS. 2 and 3

, assembly

10

comprises a housing

20

, an actuator

22

, a movable contact assembly

24

, a stationary contact board

26

and a lid

28

, in addition to connector

16

. Housing

20

is formed of suitable moldable, electrically insulative material such as plastic with an open channel

20

a

between first and second platform surfaces

20

b

,

20

c

extending from opposed end walls

20

d

,

20

e

respectively which define first and second extremities of open channel

20

a

(see FIG.

3

). The platform surfaces

20

b

,

20

c

serve as a sliding seat for the actuator to be discussed below. Opposed sidewalls

20

f

,

20

g

also form part of the actuator sliding seat arid extend between the end walls and above the platform surfaces a selected height. Walls

20

f

,

20

g

receive contact board

26

thereon and for that purpose are provided with bores

20

h

. Bores

14

a

,

14

b

, for mounting the switch system to the transmission housing wall, are provided with suitable bushings

14

c

,

14

d.

Actuator

22

, formed of suitable moldable, electrically insulative material, such as the same material used for housing

20

, is provided with a yoke

22

a

extending downwardly from base wall

22

e

and mounts movable contact assembly

24

on its upper side. Movable contact assembly

24

has a base strip

24

a

having a plurality of mounting apertures

24

b

which are received on pegs

22

b

of actuator

22

which are staked over to lock the movable contact assembly thereon. Movable contact assembly

24

has a plurality of electrically conductive, cantilever mounted, contact arms

24

c

each having a bifurcated contact tip adapted to be biased into engagement with contact board

26

which is mounted over the movable contact assembly. Spacing between the fixed base strip

24

a

of the movable contact assembly and stationary contact board

26

is determined by castellated, upstanding end walls

22

t.

Contact board

26

, formed of suitable moldable, electrically insulative material, has a plurality of spaced, linear contact paths

26

a

extending between ends

26

b

,

26

c

and separated from one another by electrically insulative ribs

26

d

. Electrically conductive contact segments

26

e

are disposed at selected longitudinal locations in paths

26

a

according to a preselected contact pattern. Contact board

26

is provided with a plurality of pegs

26

f

extending upwardly from its upper side which are received in matching bores

28

a

of lid

28

and staked thereover to lock the lid to board

26

.

Actuator

22

is received in housing

20

with yoke

22

a

extending through channel

20

a

of the housing and with spaced arms

22

c

,

22

d

of the generally U-shaped yoke

22

a

received in a reduced diameter section

12

b

of manual valve member

12

. The width of arms

22

c

,

22

d

taken in the longitudinal direction is selected to closely match the axial length of section

12

b

so that there is minimal clearance in the longitudinal direction. Lid

28

is placed over sidewalls

26

f

,

26

g

of actuator

26

and fastened to housing

20

by means of fasteners

30

received through bores

26

g

of contact board

26

and

20

h

of housing

20

. Actuator

22

is adapted to slide back and forth between first and second extremities of open channel

20

a

on the actuator sliding seat formed by platform surfaces

20

b

,

20

c

by means of motion imparted through yoke

22

a

by longitudinal movement of manual valve member

12

along axis

12

a

. Movable contact assembly

24

is connected to an electrical source (not shown) through pins

16

and is adapted to close an electrical circuit with each of the stationary contact segments

26

e

when in physical engagement therewith. As actuator

22

moves, movable contacts

24

c

slide along respective contact paths

26

a

in physical engagement therewith so that electrical engagement is effected as the contacts move into engagement with respective stationary contact segments

26

e.

With particular reference to

FIGS. 4-9

, actuator

22

has a base wall

22

e

having opposed end portions

22

f

,

22

g

and opposed side portions

22

h

,

22

i

. First and second, essentially identical beams

22

k

having a selected cross sectional area are formed in wall

22

e

by means of isolation slots

22

m

and a protrusion

22

n

is centrally formed between the ends of each beam extending downwardly from the bottom surface of each beam as seen in FIG.

9

. As best seen in

FIG. 6

, the cross sectional area of beams

22

k

is chosen, in cooperation with the length of isolation slots

22

m

and the material of the actuator, to provide a selected stiffness to the beams, allowing the beams to be deflected in the vertical direction when an upward force is applied to protrusions

22

n

as will be explained below. A protrusion

22

o

is also formed in the lower surface of wall

22

e

at each corner of the wall having a height less than that of protrusions

22

n

and serves both as a stop surface limiting the deflection of beams

22

k

as well as a sliding surface engageable with platform surfaces

20

b

,

20

c.

A third beam

22

q

is formed at side

22

i

of the actuator by longitudinally extending isolation slot

22

r

and a laterally outwardly extending protrusion

22

s

is formed centrally on beam

22

q

. Protruding ribs

22

p

, extending laterally outwardly, are formed on opposite side

22

h

and serve as a sliding surface on the inside of wall

20

g

. The distance between sidewalls

20

f

,

20

g

of housing

20

is selected to form an interference fit with actuator

22

so that beam

22

q

will be deflected laterally a selected amount when actuator

22

is placed in housing

20

.

When contact board

26

is fastened to housing

20

, beams

22

k

will be deflected vertically and beam

22

q

will be deflected laterally eliminating clearances between the actuator and the housing in the Z (vertical) direction and the Y(lateral) direction essentially.limiting movement to the X (longitudinal) direction. The width of arms

22

c

,

22

d

(along the longitudinal axis) is selected to be closely received in the reduced diameter portion

12

a

of manual valve member

12

so that longitudinal movement will be limited essentially to the movement of the manual valve member itself and with yaw about the Z direction, pitch about the Y direction and roll about the X direction essentially eliminated.

The stiffness of beams

22

k

,

22

q

, determined by the material of the actuator, cross section of the beams and the length of the respective isolation slots, is preferably selected so that the assembly will vibrate at or above 1000 Hertz, suitable for use in an automotive environment, while at the same time staying within an acceptable window of allowable frictional force required to move the actuator along the longitudinal axis by the manual valve. That is, when the shift lever is moved by the driver to select a particular gear position, the gear shift lever rotates and the detent spring snaps a roller into a detent at a fixed position. This detent lever also drives the motion of the manual valve and if too much force is needed to move the actuator the precise positioning of the mechanism will be adversely affected.

FIG. 10

shows the output signal of six different electrical switches when subjected to Z-axis vibration of sweeping from approximately 700 to 1000 Hertz at 0.44 octaves per minute using a 20 gram mass at 135° C. temperature and a scan rate of 2 mm/sec. Devices

4

-

6

, were provided with compliant features of beams

22

k

,

22

q

and devices

1

-

3

without such features. Devices

1

-

3

displayed an erratic output due to undesirable actuator motion while devices

4

-

6

displayed a stable output as a result of the compliant features of beams

22

k

,

22

q

made in accordance with the invention.

The compliant features allow the actuator to absorb vibration and permit the spring contact arms to maintain continuous engagement with the stationary contact board with a controlled contact force independent of the loading of the actuator with the result that the state of the several switches is dependent solely on the position of the manual valve regardless of vibration.

It should be understood that although the preferred embodiment of the invention has been described in order to illustrate the invention, the invention includes various modifications and equivalents to the disclosed embodiment. It is intended that the invention include all such modifications and equivalents falling within the scope of the appended claims.